1. Field of the Invention
This invention relates generally to tamper evident closures for containers, and more particularly, to a closure for such a container capable of both opening the container as well as indicating whether any tampering with the container has occurred.
2. Description of the Prior Art
Containers of the type with which the present invention is concerned include end closures which maintain the container in a sealed condition after packaging and provide a non-releasable top to indicate tampering with the container if the end closure is moved.
U.S. Pat. No. 3,261,504 discloses one type of previously known tamperproof container with a closure wherein the contents are completely sealed until a top element is turned, initiating the tearing and destruction of a tear strip by a cutting bar on the top element. This type of closure creates dispensing openings of various shapes, but upon opening is not completely detached from the container.
U.S. Pat. No. 3,463,347 discloses another closure for cans wherein a handle bar having cutting blades at each end is rotated, enabling the blades to completely sever a weakened portion in the top of the container. Since the blades are hidden under a lip, no readily ascertainable indication of tampering is provided by the structure of this patent.
U.S. Pat. No. 3,994,413 discloses an end structure for an easy open container provided with an annular guard ring having a manually adjustable punch, and a panel with a score line. To open the panel, the punch is manually pressed into the score line and the guard ring is rotated. As is the case in the previously described reference, tampering with the container is not readily evidenced.
U.S. Pat. No. 4,567,995 in the name of the same inventor as the inventor herein discloses an end closure for a container wherein an overcap with a knife blade is rotatably attached to an endcap to engage and sever a raised dispenser portion upon rotation. The raised dispenser portion provides a relatively small aperture not suitable for the free discharge of the entire contents of the container.
Thus, it is desired to provide an improved tamper evident container end closure having an easily identifiable expedient for indicating indication of tampering and also capable of opening the entire container end. The closure of the present invention includes an overcap rotatably secured to the closed end of a container and is provided with an integral channel having a knife blade at one end. Twisting of the overcap relative to the container causes the blade to engage and sever a raised hollow rib in the endcap to create a hinged lid and expose the contents for removal. Once the overcap has been rotated to any significant extent, tampering of the container is evidenced by the visible portion of the severed rib.